Lake Tana is one of East Africa’s largest freshwater bodies, yet many of its fishes are migratory and utilize in-flowing tributaries as critical spawning habitat. However, factors such as expanding water resources developments and sand mining along these rivers and streams may disrupt this ecosystem function. We monitored juvenile and adult fish abundance and water quality across five lake tributaries from August 2014 to April 2015 to examine how irrigation schemes and water quality affect assemblage and population structure. Adult assemblages were dominated by Labeobarbus cyprinids and varied between tributaries, albeit without separation by irrigation development or sand mining. Overall, adult abundances of the dominant migratory Labeobarbus species were four-fold higher below the Shini River irrigation weir than upstream. Contrastingly, juvenile abundances were often significantly higher above these structures. Juvenile abundances decreased on average by 46% along the first 1000 m of two irrigation canals, suggesting poor habitat suitability or high mortalities from water withdrawals. Water quality varied more between rivers than sampling times, but without any separation of tributaries by irrigation or sand mining. Conductivity and turbidity-related parameters had the highest correlation with adult assemblage structure and individual species abundances. These findings indicate that Lake Tana tributaries must be managed on a case by case basis, with more focus given to mechanisms allowing fish to bypass irrigation developments and the direct assessment of fish populations between sand mining and other sites.

塔纳湖是东非最大的淡水水体之一，但它的许多鱼类都是洄游的，并利用流入的支流作为重要的产卵栖息地。然而，在这些河流和溪流沿线扩大水资源开发和采砂等因素可能会破坏这种生态系统功能。2014 年 8 月至 2015 年 4 月，我们监测了五个湖泊支流的幼鱼和成鱼丰度和水质，以研究灌溉计划和水质如何影响种群和种群结构。成虫组合以Labeobarbus cyprinids为主，在支流之间变化，尽管没有因灌溉开发或采砂而分离。总体而言，占主导地位的迁徙性Labeobarbus 的成虫丰度石泥河灌溉堰下方的物种比上游高四倍。相比之下，这些结构之上的幼鱼丰度通常显着更高。在两条灌溉渠的前 1000 米处，幼鱼的数量平均下降了 46%，这表明栖息地适宜性差或取水导致死亡率高。河流之间的水质变化比采样时间更大，但没有通过灌溉或采砂来分离支流。电导率和浊度相关参数与成虫组合结构和单个物种丰度的相关性最高。这些调查结果表明，塔纳湖支流必须根据具体情况进行管理，